Cover - USD ($)	12 Months Ended
	Sep. 30, 2020	Oct. 31, 2020	Mar. 31, 2020
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Sep. 30, 2020
Document Transition Report	false
Entity File Number	1-16671
Entity Registrant Name	AMERISOURCEBERGEN CORP
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	23-3079390
Entity Address, Address Line One	1300 Morris Drive
Entity Address, City or Town	Chesterbrook,
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	19087-5594
City Area Code	610
Local Phone Number	727-7000
Trading Symbol	ABC
Title of 12(b) Security	Common stock
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 10,238,925,461
Entity Common Stock, Shares Outstanding		204,249,747
Entity Central Index Key	0001140859
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--09-30
Document Fiscal Year Focus	2020
Amendment Flag	false